LIG-10247 Add reusable multi-series bar chart

[ikondrat]

Summary

• extend BarChart with an optional, backward-compatible named-series model
• render grouped bars on a shared category axis in horizontal and vertical orientations
• derive stable series colours from series IDs
• add a scrollable ECharts legend and series-aware grouped tooltip
• zero-fill absent category values defensively
• expand the scroll extent as the number of series grows
• register the legend component in existing chart test mocks

Stack

• Base: LIG-10239 Wire sample-tag distribution comparison #1695 (LIG-10239 comparison selection and query wiring)
• This PR: LIG-10247
• Follow-up: LIG-10240 adapts distribution data and integrates the primitive

This split keeps the reusable chart change below the requested 150-line threshold.

Testing instructions

1. Check out this branch with the preceding stack.
2. Run:

   cd lightly_studio_view
   make static-checks
   npm run test:unit -- --run \
     src/lib/components/BarChart/buildEchartsOption.test.ts \
     src/lib/components/BarChart/BarChart.test.ts \
     src/lib/components/DatasetDistributionPanel/DatasetDistributionPanel.test.ts \
     src/lib/components/DatasetDistributionPanel/ExpandDialog/ExpandDialog.test.ts

3. Pass multiple CategoryCountSeries values to a BarChart and verify grouped bars, legend scrolling, tooltips, both orientations, and chart overflow.
4. Remove series and verify the existing single green series and percentage tooltip are unchanged.

Validation

• make static-checks: passed
• 43 focused unit tests: passed

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch kondrat-lig-10247-frontend-reusable-multi-series-bar-chart-primitive

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